Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P61278 (somatostatin)
 22,083 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of glucagon suppression by somatostatin upon endogenous hyperglycemia was studied in three forms of experimental insulin deficiency in dogs: alloxan diabetes, total pancreatectomy, and diazoxide administration. In six insulin-requiring alloxan-diabetic dogs deprived of insulin for 24 hr, mean plasma glucose declined to 77% +/- 6% of the baseline level of 350 +/- 41 mg/dl during 3 hr of glucagon suppression, significantly below the unsuppressed saline controls (p less than 0.01-0.05). When somatostatin was discontinued, glucagon rose and glucose increased 21% (p less than 0.05) in 30 min. Significant correlation between maximal changes in glucagon and glucose was observed (r = 0.81; p less than 0.001). Even during a 1-hr alanine infusion in such dogs, glucose declined an average of 36 +/- 9 mg/dl, instead of rising 51 +/- 7 mg/dl as in unsuppressed controls. Maximal changes in glucagon and glucose were correlated (r = 0.85; p less than 0.01). In eight depancreatized dogs pretreated intravenously with continuous insulin and glucose infusions, withdrawal of insulin was followed by a rise in extrapancreatic glucagon; mean plasma glucose rose from 212 +/- 43 to 415 +/- 80 mg/dl 270 min after the end of the insulin infusion. However, when glucagon was suppressed after insulin withdrawal, glucose remained below 240 mg/dl, significantly less than the controls (p less than 0.005); when somatostatin was stopped, glucagon rose and glucose increased 88 +/- 19 mg/dl within an hour. The rises in glucagon and glucose were significantly correlated (r = 0.68; p less than 0.05). Glucagon suppression by somatostatin during diazoxide-induced blockade of insulin secretion in four normal dogs reduced hyperglycemia significantly but did not prevent it. The results support the hypothesis that a relative or absolute excess of glucagon, as well as a relative or absolute deficiency of insulin, is etiologically important in the development of endogenous hyperglycemia in diabetes mellitus, the hyperglucagonemia probably mediating the glucose overproduction.
 ...
PMID:The role of glucagon in the pathogenesis of the endogenous hyperglycemia of diabetes mellitus. 118 99

Plasma glucose and glucagon responses to standard meals containing carbohydrate, fat, and protein as in normal diets were studied in 12 subjects with insulin-dependent diabetes and 12 normal subjects. Diabetics had two to three times greater glucagon responses than did normal subjects. Fifteen units of insulin injection did not normalize these excessive glucagon responses, although postprandial hyperglycemia was reduced. Infusion of somatostatin at a dosage of 500 mug/hr prevented glucagon responses and diminished postprandial hyperglycemia by 60%. The combination of insulin and somatostatin caused a progressive fall in plasma glucose levels despite meal ingestion. Somatostatin and insulin, administered subcutaneously in the same syringe, also abolished postprandial hyperglycemia. These studies indicate that excessive glucagon secretion participates in the genesis of diabetic postprandial hyperglycemia. Somatostatin, an inhibitor of glucagon secretion, may thus prove useful as an adjunct to insulin in the treatment of diabetes mellitus.
 ...
PMID:Abnormal pancreatic glucagon secretion and postprandial hyperglycemia in diabetes mellitus. 124 53

We studied the effect of adrenergic blockade on hepatic venous hyperglycemia and the activation of a hepatic glycogenolytic enzyme, phosphorylase-a, in response to cerebral cholinergic activation. Neostigmine was injected into the third cerebral ventricle of bilaterally adrenodemedullectomized (ADMX) rats, while somatostatin and insulin were administered intravenously. Hepatic venous plasma glucose concentrations and hepatic phosphorylase-a activity were measured. Intracerebroventricular injection of neostigmine (5 x 10(-8) mol) caused increases in hepatic venous glucose concentrations and hepatic phosphorylase-a activity. Both of these changes were prevented by intraperitoneal (IB) pretreatment with phentolamine (5 x 10(-7), 1 x 10(-6) mol) without the intervention of insulin secretion, but not by pretreatment with the alpha-adrenoreceptor antagonist phenoxybenzamine (1 x 10(-6) mol), the beta-adrenoreceptor antagonist propranolol (1 x 10(-6) mol), the alpha 1-antagonists prazosin or bunazosin (1 x 10(-6) mol), the alpha 2-antagonist yohimbine (1 x 10(-6) mol), or prazosin (5 x 10(-7) mol) plus yohimbine (5 x 10(-7) mol). These results suggest that phentolamine prevented brain-mediated hepatic glycogenolysis by a mechanism that may not be classified pharmacologically as involving either alpha 1- or alpha 2-receptors.
 ...
PMID:Effects of adrenergic blockers on central nervous system-mediated hyperglycemia in fed rats. 135 Mar 17

Systemic drainage of pancreatic venous effluent and denervation of the pancreas that follows pancreatic transplantation has been shown to alter postoperative glucose disposal despite elevated levels of peripheral insulin in response to a glucose challenge. Since an appreciable fraction of postprandial glucose disposal takes place in the absence of insulin (insulin-independent glucose disposal--IIGD), we have investigated potential changes in this aspect of carbohydrate metabolism before and after bladder-drained pancreatic auto-transplantation (PAT/B) as well as partial pancreatectomy (PPx). The hyperglycemic clamp protocol with a background infusion of somatostatin was performed on control (PREOP) dogs as well as PAT/B and PPx animals. The rate of glucose disposal (M Value) during the period of hypoinsulinemia induced by Somatostatin (SST) was measured and reported. Whereas glucose disposal during steady state hyperglycemia was significantly diminished for both PPx and PAT/B in the absence of SST, IIGD was unaltered across all three groups studied. We therefore conclude that surgical alteration of the pancreas results in abnormal glucose disposal during steady state hyperglycemia despite apparently normal to supranormal levels of peripheral insulin, and that alterations in IIGD are not responsible for these differences.
 ...
PMID:Surgical alterations of the pancreas and insulin-independent glucose disposal. 135 66

Acute hyperglycemia inhibits the growth hormone (GH) response to several stimuli including growth hormone-releasing hormone (GHRH), likely acting by stimulation of endogenous somatostatin release. The aim of our study was to verify whether arginine ([Arg] 30 g intravenously [IV] in 30 minutes), a well-known GH secretagogue likely acting via inhibition of hypothalamic somatostatin release, counteracts the inhibitory effect of oral glucose (OG) administration (100 mg orally) on the GH response to GHRH (1 micrograms/kg IV bolus) in seven normal subjects (aged 20 to 30 years). The GH response to GHRH (peak, 11.6 +/- 1.8 micrograms/L) was inhibited by previous OG load (peak, 7.4 +/- 0.8 micrograms/L; P less than .02 v GHRH alone) and potentiated by Arg coadministration (peak, 36.2 +/- 8.8 micrograms/L; P less than .03 v GHRH alone). The potentiating effect of Arg on the GHRH-induced GH increase was unaffected by previous OG load (peak, 30.4 +/- 6.9 micrograms/L). In conclusion, our results show that Arg abolishes the inhibitory effect of OG administration on the GHRH-induced GH response in man. These data, although indirect, suggest that both acute hyperglycemia and Arg act at the hypothalamic level, stimulating and inhibiting, respectively, the release of somatostatin.
 ...
PMID:Arginine abolishes the inhibitory effect of glucose on the growth hormone response to growth hormone-releasing hormone in man. 135 80

A highly active cyclic hexapeptide analogue of somatostatin, Cyclo(N-Me-L-Ala-L-Tyr-D-Trp-L-Lys-L-Val-L-Phe), L-363,586, was found to improve the control of postprandial hyperglycemia in diabetic animals when given in combination with insulin. The compound is reported to be relatively stable in blood, nasal cavity, and intestinal lumen but undergoes rapid degradation in aqueous solution. The objective of this study was to elucidate the degradation mechanisms based on the kinetic data and the structure of the degradation products. Both pH and temperature had a profound influence on the instability of the peptide in aqueous solution. The data indicated that the peptide was most stable at a pH of about 4.7. The pH-rate profile exhibited specific acid catalysis at a pH less than 3.0 and base catalysis above pH 10.5. The kinetic pKa was determined to be 9.7. This pKa could be attributed to the tyrosine residue. The mechanisms of degradation under acidic and alkaline conditions appear to be different. Identification of the fragments obtained using mass spectrometry and amino acid sequencing suggest that the cyclic compound was cleaved to yield a linear fragment, which underwent further cleavage at both peptide linkages alpha to the tryptophanyl residue. The indole group of that residue is probably the potential nucleophile attacking the adjacent carbonyls. A rate equation for the degradation of the hexapeptide has been proposed.
 ...
PMID:Kinetics and mechanism of degradation of a cyclic hexapeptide (somatostatin analogue) in aqueous solution. 136 Jan 56

The strain of athymic nude male mice (ANM) developed at the University of Southern California (USC) exhibits spontaneous hyperglycemia and relative hypoinsulinemia in vivo. To investigate factors that influence insulin secretion in this animal model of non-insulin-dependent diabetes mellitus, we utilized the isolated perfused mouse pancreas of the ANM-USC and control BALB/c mice. We compared in vitro glucose-induced insulin secretion in ANM-USC and control mice, inhibition of secretion by somatostatin, and variability of insulin secretion over the two-year period it took to complete these experiments. Glucose-induced insulin secretion from the isolated pancreas was biphasic in both ANM-USC and controls. Insulin secretion was quantitatively equal to or greater than control mice, depending on the phase of secretion analyzed and the source of the control mice. In contrast to pancreases of control mice, insulin secretion from ANM-USC pancreases was relatively resistant to inhibition of insulin secretion by somatostatin. Variability in insulin secretion over the two years in which these experiments were performed was greater from pancreases of control than that observed from pancreases of the ANM-USC. The hyperglycemic ANM-USC mouse does not demonstrate diminished insulin secretion in vitro yet is relatively hypoinsulinemic in vivo. Thus circulating factors other than somatostatin might contribute to the insulinopenic stage in this animal model.
 ...
PMID:Hyperglycemic athymic nude mice: factors affecting in vitro insulin secretion. 136 39

Abnormal growth hormone (GH) and adrenocorticotropic hormone (ACTH)/cortisol secretory patterns in response to a glucose load have been observed in underweight anorectic women. The present study was performed in an attempt to establish whether changes in the hypothalamic/pituitary sensitivity to hyperglycemia occur in bulimia in the absence of weight disturbance. Therefore, serum GH, plasma cortisol, and plasma insulin concentrations were measured in eight women with normal weight bulimia and in eight normal women during an intravenous glucose (0.33 g/kg as an IV bolus) tolerance test (IGTT). In addition, since abnormal pituitary hormone responses to a glucose load might reflect alterations in somatostatin (SRIH) release, TSH secretion also was measured, in view of its sensitivity to SRIH inhibition. Both GH and cortisol levels progressively and significantly declined during IGTT in the normal subjects. In the bulimic women, cortisol levels remained unchanged, whereas GH concentrations rose significantly after glucose injection. Plasma cortisol and serum GH levels were significantly higher in the bulimic than in the control subjects. No significant differences between groups were observed in hyperglycemia-induced insulin increments or in TSH decrements. These data indicate that an altered sensitivity to hyperglycemia affects the hypothalamic/pituitary centers controlling the secretion of the counterregulatory hormones GH and ACTH/cortisol in bulimia nervosa. The lack of a simultaneous change in the TSH secretory pattern argues against a possible involvement of SRIH in the pathophysiology of this disorder.
 ...
PMID:Abnormal growth hormone and cortisol, but not thyroid-stimulating hormone, responses to an intravenous glucose tolerance test in normal-weight, bulimic women. 136 37

This article is divided into two parts. A retrospective overview summarizes some of the work that provided the framework and tools of the more recent studies. The five novel areas of research are related to the indirect effects of insulin. Regulation of plasma glucose is of central importance in health and diabetes. Understanding this precise regulation requires sensitive isotope dilution methods that can measure the rates at which glucose is produced by the liver and used by the tissues on a minute-to-minute basis. Validation studies indicated that the non-steady-state tracer method yields reasonable results when the specific activity of plasma glucose does not change abruptly. During hyperinsulinemic glucose clamps, the decrease in specific activity of glucose can be prevented by the MSTI. During exercise, the decrease of specific activity can be only in part ameliorated by step-tracer infusion. Depancreatized dogs are used extensively as a model of selective insulin deficiency, because dog stomach secretes physiological amounts of glucagon. This strategy can avoid injections of somatostatin, which can have other affects in addition to the suppression of insulin and glucagon. In human diabetes, in addition to an increase of glucose production, there is also an increase in glucose cycling in the liver. In animal models of diabetes, mild NIDDM, and in glucose intolerance, the percentage of increments of glucose cycling are much larger than those of glucose production. We hypothesize, therefore, that measurements of glucose cycling can be used as an early marker of glucose intolerance. Application of different tracer strategies and use of the depancreatized dog as a model of diabetes, we investigated the importance of the indirect effects of insulin in the pathogenesis of diabetes. 1) Because, in the treatment of IDDM, insulin is administered by the peripheral routes we compared the relative importance of hepatic and peripheral effects of insulin in regulating the rate of glucose production. Experiments were performed in depancreatized dogs that were initially maintained at moderate hyperglycemia (10 mM) with subbasal portal insulin infusion. During the experimental period, insulin was infused either peripherally or portally at 0.9 mU.kg-1.min-1. In addition, peripheral infusions were also given at 0.45 mU.kg-1.min-1. We concluded that when suprabasal insulin levels are provided to moderately hyperglycemic depancreatized dogs, the suppression of glucose production is more dependent on peripheral than portal insulin concentrations. This indirect effect of insulin may be mediated by limitation of the flow of precursors and energy substrates for gluconeogenesis and/or by suppressive effect of insulin on glucagon secretion.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:Banting Lecture: glucose turnover. A key to understanding the pathogenesis of diabetes (indirect effects of insulin). 149 70

In awake rats adapted to experimental conditions and allowed food ad libitum, hyperglycemia was induced by the administration of morphine 10 mg/kg through indwelling catheters in the external jugular vein. High glucose values were measured at 5, 15 and 25 min. Glucagon values were high at 5 and 15 min, and again at basal level at 25 min. Insulin was increased after morphine both at 5, 15 and 25 min, whereas somatostatin levels did not change after morphine. When morphine was administered together with naloxone after an initial 10 min period of naloxone administration, there was no increment in glucose, insulin or somatostatin values; neither at 5, 15 or 25 min. There was a remarkable glucagon decrease after naloxone and morphine remaining from 5 to 25 min. Then, one of the possible mechanisms for the hyperglycemic response after morphine may be an opioid effect on pancreas, stimulating glucagon and thereby causing hepatic glucose output.
 ...
PMID:Increments in glucose, glucagon and insulin after morphine in rats, and naloxone blocking of this effect. 152 92


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>